Retroreflective structures of the type utilized herein are described in detail in the Jungersen U.S. Pat. No. 2,380,447, issued Jul. 31, 1945, the Hoopman U.S. Pat. No. 4,588,258, issued May 13, 1986 and the Stamm U.S. Pat. No. 3,712,706, issued Jan. 23, 1973 (each of which is incorporated herein in its entirety by reference.)
Walter, U.S. Pat. No. 5,171,624 discloses microprism reflective sheeting in which prism pairs are tilted with respect to one another at an angle of 3-10.degree., a prism size of 0.006-0.025 (space between apices) and wherein at least one prism side surface is arcuate.
Benson U.S. Pat. No. 5,122,902 discloses retroreflective cube-corner elements with separation surfaces between elements and truncated cube-corner elements.
Conventional retroreflecting prism or corner cube arrays of the type described in U.S. Pat. No. 5,171,624 (incorporated herein by reference in its entirety) create a diffraction pattern having a characteristic void outside of a central maxima and a six lobed light energy distribution. The six lobes of energy formed about the central maxima represent the energy cones of the first order of diffraction. Such an energy distribution is undesirable because of the high degree of variation of energy level throughout the retroreflected beam.